Marantz 3800 User manual

manuaL
MODEL
3800

ERR
ae
Heaan
ER
UZ:
MODEL
3800
SERVICE
MANUAL
MARANTZ
CO.,
INC.
20525
NORDHOFF
STREET,
CHATSWORTH,
CALIFORNIA
91311
A
WHOLLY
OWNED
SUBSIDIARY
OF
SUPERSCOPE
INC.,
CHATSWORTH,
CALIFORNIA
91311

SECTION 1
GENERAL INFORMATION AND OPERATING PRINCIPLES ..... 0... ccc cece cece cece rete enennes
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3. DESCRIPTION AND OPERATION... 0.0... ccc ccc cece reece teen e tenant eeeeeene
A. FUNCTIONAL DESCRIPTION .. 0.0... ccc cece ee eee teen eee
B. OPERATING PRECAUTIONS ......... 0c cece ccc eee eee etre neat eee
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D. PHONO/MIC AMPLIFIER... .... cece cc cee een teeta eens
E. DOLBY ENCODE / DECODE PROCESSORS... 2... ... ccc ect eeetee ee eens
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G. ACTIVE FILTER NETWORK... 1... ccc cece ee eee eee ee renee
H. TONE CONTROL / TURNOVER NETWORK.......... cee eee e ee teen ete eee eee ene
4. DOLBY NOISE REDUCTION CIRCUIT ...... 0. ccc ccc cece eee eter reenter teenie
A. BASIC DOLBY PROCESS ....... cece ccc cece ee eee eee e nett e ene
B. USE OF THE DOLBY (NR) CIRCUIT AS A DYNAMIC NOISE FILTER............0.00 eee
5. TECHNICAL SPECIFICATIONS ..... 0... eee cece renee eee nee tetera ee eee
SECTION 2
MAINTENANCE ..... 0 cc cc cece ee ce eee eee cence eee ee eee eee eee eee nano e tree senna eae
1. GENERAL... 1... cic ee ce ce erent cece ete n eee e terete teen ete cee nenes
2. PREAMPLIFIER CIRCUITS TESTS AND ADJUSTMENTS ......... 00. e eee ee eee erences
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B. PRELIMINARY CONDITIONS . 2.0.2.0... ccc ccc cece eee nent eens
C. POWER CONSUMPTION VERIFICATION ......- 0.0. cece cece eee eee
D. FUNCTIONAL TEST ......... 00. cece cee eee reece nee nett a tenet eeenenee
E. MAXIMUM VOLTAGE OUTPUT ..... 0... cece cee eee teen ene enennes
F. TOTAL HARMONIC DISTORTION (THD) ...... 2... cece ce cee cece eee eens
G. HUM AND NOISE... 2... ec ccc cece eee tn cern een e ene e eee en eee een eenne
H. FREQUENCY RESPONSE (PHONO /MIC).......... 0.26 c ee eee eens
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N. VOLUME TRACKING... . ccc cee ee renee ee eee eee teens
P. LOUDNESS CONTOUR... cece cc ee eee teen e ne nneee Aaa Ren ceays. uate
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TABLE OF CONTENTS
2-1
2-1
2-1
2-1
2-1
2-3
2-3
2-4
2-4
2-4
2-4
2-5
2-5
2-7
2-7
2-7
2-7
2-8
2-8
2-8
2-9
2-9

TABLE OF CONTENTS
( continued )
SECTION 2 PAGE
E. DOLBY RECORD MODE FREQUENCY RESPONSE........... 00. c cece cece eee ee tenes 2-9
F. DOLBY PLAYBACK MODE FREQUENCY RESPONSE .......... 20. - cee e cece eee eee eee 2-10
G. TOTAL HARMONIC DISTORTION (THD) ,..... 0... . eee cee te eee ee tee ene e eee 2-12
H. DOLBY VU METER CALIBRATION .... 0... cc ccc cece cece cece ete eet eens 2-13
J 400 Hz TONE OSCILLATOR ADJUSTMENT ....... cece cece ee eee eee ene eee 2-13
K. MULTIPLEX FILTER ADJUSTMENT... ccc cece cece eee cece eee een eens 2-13
LE. BIAS: FILTER ADJUSTMENT 02 ccc see cee tens earned nents sented bene ee eena tates 2-13
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5. REPACKING FOR SHIPMENT ......... 2 cece cece ce cece cee eee eee teen e eee eens 2-15
SECTION 3
ILLUSTRATED PARTS LIST... 2. ccc ccc c ccc cc cen ccc n cnn tec e rete rene tense ee een een eneesneeeseesese 3-1
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MODEL 3800 STEREO CONTROL CONSOLE UNIT (PREAMPLIFIER) .......-. ccc eee acne eee 3-1
CHASSIS: ASSEMBLY nie: cisysis.5 weal ole Gaye's eee iewe wie erelaied Blebin eck, Mebane eigen de tea eee 3-5
CONTROL BOARD COMPONENT ASSEMBLY ........ 0 cece e ere cece tne ete eee e ete e nee 3-6
PREAMPLIFIER BOARD COMPONENT ASSEMBLY ........ 0... cece eee ee ee eee teenie 3-9
JACK PANEL ASSEMBLY 2.01. ss disses oe Si 25 ele eee sie aje Cave CE ead ee Be 3-11
DOLBY - TAPE MONITOR BOARD COMPONENT ASSEMBLY ....... 0. cee esse cert e eee e ene 3-12
TAPE EQUALIZATION - TONE DEFEAT BOARD COMPONENT ASSEMBLY ..........-.++---- 3-15
400 Hz OSCILLATOR - DOLBY METER BOARD COMPONENT ASSEMBLY.............0000-- 3-16
INTERFACE BOARD COMPONENT ASSEMBLY ........ 0... s eee eee cece eee eee e eee eee 3-16

FIGURE NO.
1-1
1-2
1-3
1-4
a
2-2
2-3
2-4
2-5
2-10
2-11
31
3-2
3-3
34
3-5
3-6
37
38
39
TABLE NO.
1-1
1-1
2-1
2-2
2-2
2-2
LIST OF ILLUSTRATIONS
TITLE
Functional Block Diagram... 02.0.0. cece ce cece eect eeeeunuuuee
Wiring Diagrarnts ieee ocd 5 sace vrs a ets dent die eit ey wee oo S sack daiwa Shaiara leas Meese
Dolby NR Circuit Signal Processing Diagram ........... 0.00 cece eee eees
Dolby NR Circuit Signal Processing Diagram (continued) ...............0005
AC Power Control Box Connection Diagram... . 0.0... ccc cee cece cece eceees
Test Equipment Connection Diagram, Preamplifier Circuits............200e005
RIAA Equalization Curve and Standard ......... ccc cc cece cece cee cceceaeeue
Active Filter Network Characteristics ..... 0.0.0. 0c cece cece ce ceuuvetvvenee
Dolby Frequency Response, Flat Mode ...........cccc sec e ccc eeaueceesees
Dolby Frequency Response, Encode Mode..........cccceuccecucevcececece
Dolby Frequency Response, Decode Mode..........00ccccececccecsavasecs
Repacking Illustration... 0.0... ccc cc cece cee ence ne eeeenseueenes
Front Panel Controls and Indicators... 1... .. 2c. cece cece ccc cence een eeaes
Rear Panel Jacks and Connectors .... 0.0... cs ccc eee e cece neces eeeenauens
Disassembly / Reassembly Diagram.... 2.0... 0c. ceca cece cc ccecectcecece
Control Board Diagram, Circuit Side... .. 0... ccc cc eee eee ne eeaee
Preamplifier Board Diagram, Circuit Side. ...... 0... cece eae eee eee neeee
Dolby - Tape Monitor Board, Circuit Side... .. 2... cee ee cee cece ee
Tape Equalization - Tone Defeat Board, Circuit Side........... ccc cece ee aces
Tone Oscillator - Dolby Meter Board, Circuit Side.... 00... cc cee eee eee eee
Schematic Diagram ........ 0. cece cece ccc ete e ee eee ence nee nnnneege
TITLE
Recommended
Test
Equipment............ccee
cece
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Trouble
Analysis...
2.0.2.0...
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ence
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PAGE
1-3
1-4
1-5
1-6
2-2
2-2
2-5
2-6
2-6
3-14
314
PAGE
1-8
1-9
2-3
213
214
215

Section 1
GENERAL
INFORMATION
AND
OPERATING
PRINCIPLES
|
1. INTRODUCTION
This manual was prepared for service technicians
in factory-authorized warranty repair stations and
other equally-qualified and equipped service cen-
ters. The service information contained herein is
applicable to the Model 3800 Stereo Control
Console, a stereo preamplifier manufactured by
the Marantz Company, Inc., a subsidiary of
Superscope
Incorporated,
Chatsworth,
California
91311.
2. GENERAL
Section 1 describes physically and functionally the
Model 3800 Stereo Control Console,a professional,
state-of-the-art stereo preamplifier with the Dolby
noise reduction (NR) circuit. Use, application,
performance and design features are also described.
Mechanical parts are high-quality, selections for
reliability and economy. Electronic components
in the Model 3800 circuits are precision devices
selected for their long operating life. The Model
3800 is thereby assured of providing continuous
high-quality performance.
System, functional, and detail descriptions include
the major mechanical functions and control
electronics. Specifications and capabilities are
both technical and performance related.
3. DESCRIPTION AND
OPERATION
This section is included to assist the service tech-
nician in understanding the operation of the
Model 3800. The technical data describe the basic
system functions and circuit theory of operation.
A.FUNCTIONAL DESCRIPTION
F igure 1-1 is a Functional Block Diagram of the
Model 3800 left audio channel, showing the
principal circuit elements and signal flow paths.
Additional functional and detailed reference
support data are illustrated on Figures 1-2
through 1-4: Wiring, and Dolby NR Circuit
Signal Processing Diagrams, respectively.
B. OPERATING PRECAUTIONS
WARNING:
TO
PREVENT
FIRE
OR
SHOCK
HAZARD,
DO
NOT
EXPOSE
THIS
INST
RU-
MENT
TO
RAIN
OR
MOISTURE.
CAUTION: ENSURE THAT THE TOTAL
POWER OUTPUT CONNECTED TO THE
SPEAKER SWITCHING INPUTS DOES NOT
EXCEED 250 WATTS RMS PER CHANNEL,
CONTINUOUS POWER.
CAUTION: DO NOT EXCEED THE MAXI-
MUM TOTAL POWER RATINGS OF THE
AC OUTLETS. THE POWER SWITCH AND
OTHER CIRCUITRY IN THE MODEL 3800
MAY BE DAMAGED IF SUBJECTED TO
EXCESSIVE CURRENT.
CAUTION: TURN VOLUME CONTROL CCW
TO MINIMUM BEFORE SWITCHING SPE AkK-
ER UNITS TO PREVENT POSSIBLE DAM.-
AGE TO YOUR LOUDSPEAKERS.
C. SYSTEM OPERATION
High- and low-level inputs (program sources) are
selected by the Program Selector Pushswitches
and applied in accordance with signal level.
When low-level sources are selected (PHONO or
MIC), the Program Selector Pushswitch applies
the input signal to the Phono/Mic Amp) fier
circuit and selects the proper equalization,
RIAA or Mic. The output of the Phono/Mic
Amplifier
is
then
returned
to
the
Prog-am
Selector Pushswitches where it is handle# as
another high-level input.
High-level input signals TUNER, AUX, TAPE 1,
TAPE 2 or the output of the Phono/Mic An pii-
fier are applied to the Dolby encoder/dec) der
4-1

1-2
through the buffer amplifier circuit, TAPE
REC-EQ and DOLBY Switches. The input level
to the encoder/decoder is regulated by the
RECORD LEVEL Controls. The output of the
encoder/decoder is applied to the TAPE OUT-
PUT and DUBBING OUT Jacks. With the
DOLBY Switch set to OF F, the encoder/decoder
is bypassed and the high-level input signals are
applied directly to the TAPE OUTPUT and
DUBBING OUT Jacks. The encoder/decoder
functions as a flat amplifier, an encoder, or a
decoder depending on the position of the
DOLBY
Switch
(Figures
1-1
and
3-9).
The high-level input signals are concurrently
applied to the SCOPE OUTPUT Jacks and to the
Dolby decoder, through the TAPE MONITOR
Switch and PLAY CAL Controls. The decoder
functions as a flat amplifier, or a decoder, de-
pending on the position of the DOLBY Switch,
the TAPE MONITOR Switch, and the TAPE
COPY Switches (Figure 1-1). The output signal
of the decoder is monitored by the Dolby Level
VU Meter and applied to the MODE Switch.
The MODE Switch determines the manner in
which the left- and right-channel signals of the
program source are applied in the Model 3800:
LEFT channel only, RIGHT channel only, two-
channel STEREO, STEREO REVERSE, or
L+ R (left and right channels combined). The
signal selected by the MODE Switch is then
applied to the BALANCE Control. The
BALANCE Control adjusts the relative signal
level of the left and right channels by attenuating
the level of one channel while maintaining the
level of the other. From the BALANCE
Control, the signal is applied to the VOLUME
Control, which varies the level of the output
signal available at the PREAMPLIFIER OUT-
PUT Jacks.
The signal is also applied to the Loudness
Contour Circuit which, when activated, boosts
low and high frequencies at low listening levels
so that all frequencies appear to have equal
loudness. The Loudness Contour Circuit adjusts
the frequency response of the Model 3800 to
compare with the Fletcher-Munson loudness
curves (Section 2). The signal from the
VOLUME Control is then applied to the input
of the Times-Ten (X10) Amplifier Circuit.
The X10 Amplifier increases the signal level to
that required to drive power amplifiers. The
output of the X10 Amplifier is applied to an
Active Filter Network comprised of three filter
circuits (30Hz, 5KHz and 9KHz) and a Filter
Amplifier.
The
Active
Filter
Network
sharply
reduces
low-
and/or
high-frequency
noise
that
may
originate
at
the
program
source.
The
out-
put
of
the
Filter
Amplifier
is
then
applied
to
the
Tone
Control/Turnover
Network
(BASS,
MID
and
TREBLE
Tone
Controls),
the
250Hz
and
the
4KHz
TURNOVER
circuitry,
and
a
Tone
Amplifier
stage
(through
the
TAPE
REC-EQ
Switch).
The
output
of
the
Filter
Amplifier
after
TAPE
REC-EQ
is
also
applied
to
the
TONE DEFEAT Switch.
The
Tone
Control/Turnover
Network
performs
a
dual
function:
the
tone
control
portion
of
the
network
boosts
or
attenuates
low,
middle
and
high
frequencies;
the
turnover
portion
of
the
network,
when
activated,
decreases
the
point
at
which
low
frequencies
are
affected
by
the
BASS
Control
(250Hz)
and
increases
the
point
at
which
high
frequencies
are
affected
by
the
TREBLE
Control
(4KHz).
The
TONE
DEFEAT
Switch
selects
either
the
flat
output
of
the
Filter
Amplifier
(bypassing
the
tone
controls)
or
the
tone-control-altered
output
of
the
Tone
Amplifier.
From
the
TONE:
DEFEAT
Switch,
the
signal
is
applied
to
the
Time
Delay
Relay.
The
circuit
associated
with
the
Time Delay
Relay
holds.the
relay
contacts
open
for
approx-
imately
five
seconds
after
power
is
appied
to
the
Model
3800.
After
the
power
supply
circuits
have
stabilized,
the
relay
contacts
close.
Audible
“pops”
that
may
arise
from
p
ower
supply
transients
are
thereby
eliminated.
From the relay contacts the signal is appied to
the PREAMPLIFIER OUTPUT Jacks and con-
nected to drive an external power aml ifier.
The
power
amplifier
outputs
are
connecied
to
the
SPEAKER
SWITCHING
INPUTS
Terminals
and
the
signal
is
applied
to
the
stereo
PHD
NES

IN
PROGRAM
SELECTOR
OUT
PHONO
1
IN
Cc
A.
0201
Q203
205
207
209
PHONO 2 IN Cc
pes
PHONO/MI'
AMPL,
PHONO/MIC
EQUALIZATION)
t.
BFR
TO
TAPE
REC-EQ
SW
BUFFER
AMPL
MIC IN
TO
TAPE
REC-EQ
SW
RCD
LVL
CONT
TONE
CONTROL/TURNOVER
NETWORK
501
TUNER
IN
ACTIVE
FILTER
NETWORK
u201
211
30 Hz 9 KHz 5 KHz
FILTER FILTER FILTER
AUX
IN
-
A
CIRCUIT
CIRCUIT
CIRCUIT,
DOLBY
eNcopeR /o
DECODER
FEEDBACK
TAPE
TIN
&
CIRCUIT
P
=
TAPE
21N
(céstwer)
me
TURNOVER
°
FILTER
Ds
CIRCUITS
DUBBING IN
FROM L CHAN
DUBBING
OUT
a
°
TO
RIGHT
CHANNEL
0
DOLBY
° 9
BALANCE
TAPE
1
OUT
pecourn
9
FROM R CHAN 1]
5
. 4
'
TAPE2OUT
=
SIDE
CHAIN
|
i
INPUT
a
:
H
ad
SCOPE
CUT
Cc
DOLBY:
'
[votume]
.
10
R
CHAN
METER
TtRo
S
0
acca
STEREO REVO i
=
H
SPEAKER
STEREOO
&
'
|
SWITCHING
t
1
RIGHTO
¥
‘st
LOUDNESS
INPUTS
Lert
‘SS
CONTOUR
@
™
CIRCUIT
‘0
af
oo
0
-O—
Pra
PRIAMP
COUT
SPEAKERS
out
«LOUDNESS
}>
IN
REMOTE
SPEAKERS
PHONES
Figure
1-1
Functional
Bhck
Diagram
1-3

LS
A100 CONTROL BOARD
P/N 200-2002-100
CHASSIS FRONT
CHASSIS BASE
A500 DOLBY/TAPE
MONITOR BOARD
P/N 200-2003-100
7 CONDUCTORS (TWISTED)
3 CONDUCTORS (TWISTED)
A200/300 PREAMPLIFIER BD 3 CONDUCTORS (TWISTED)
OO O O PIN 200-2009-100
3 CONDUCTORS (TWISTED)
A200/300 PREAMPLIFIER BOARD
P/N 200-2009-100
CHASSIS REAR
A500 DOLBY/TAPE
MONITOR BOARD
P/N 200-2003-100
©@
A400 JACK INPUT PANEL
P/N 200-2005-110
©O
NOTES :
7 CONDUCTORS (TWISTED)
Figure 1-2 Wiring Diagram
1-4
2. FOR SCHEMATIC SEE FIGURE 39.
3800 EXPORT ONLY
220V CONVERSION
NOTE:
FOR 100V CONVERSION
CONNECT VIO JUMPER TO
WHT/YEL TRANSFORMER LEAD
ON TB6.
1. FOR COMPONENT IDE. TIFICATION REFER TO PARTS LIST.
a
u
z
e
=
=

TAPE
TAPE
TAPE
OUT
TAPE
IN
COPY
MONITOR
(TO
RECORDER)
|(FROM
RECORDER)
OUT
POSITION
POSITION
OUT
SOURCE
1——+ 2
DOLBY SWITCH
DOLBY
F
ANAL
MULE
KU
UY
WU
RUNS
AIAIAIA
NOTES:
Dolby
FM
position
pre-
Signal
from
empts
all
other
program
recorder
No.
1
SOURCE
sources.
XY
NN
1. Dolby encoder in flat
amplifier mode.
UX
RUS
x
2——+ 1
2. Dolby decoder in Si
gnal from NY
decode
mode.
recorder
No.
2
SOURCE
Ap
<|
3. ame
Decoded signal
XY?
RUN
IY
Flat
signal
SOURCE
lu
AINAIATATA
Fiat Dolby Processed signal
Ez
IL
XX
X
My
UX
NUR
i
Rt
RNS
AIAIA
SOURCE
SOURCE
NOTES:
an
Ue
Ne
X
NUS
NNN
X
1. Dolby encoder in
flat amplifier mode.
x
2. Dolby decoder in
decode amplifier mode.
Signal from
recorder No.
tee fs
I
UU
x
x
NUS
Rae
ALATATATATAJALA
XL
X
SOURCE
it
ie
X
Kk
KI
X
XY)
Figure
1-3
Dolby
NR
Circuit
Signal
Processing
Diagram
1-5

DOLBY SWITCH
REC I
TAPE TAPE TAPE OUT TAPE IN PAEAME
COPY MONITOR (TO RECORDER) |(FROM RECORDER)
POSITION
POSITION
OUT
ou
- a ae
SOURCE
—-.» 2
Oo.
Source
Signal
(YUU
RO:
RUN: NUN:
AVILA
Me
AAO
NOTES:
X
1
ign
recorder No. 1
1.
Dolby
encoder
in
Signal
from
encode mode.
x ig
un
2. Dolby decoder in
decode mode or flat
amplifier mode.
x
AUS
UU Hh
2—+- 1
Signal from
recorder No. 2 SOURCE
X
ULL
i
HN in
VV
XX
Xp
a
ANIL ALI
OUT
Encoded input
from Aux.
AIAII EL A
MAIALA
AIAIMAJADS
VV
AIAIATA
KAA
NOTES:
IA
AAA
1. Dolby encoder in
decode mode.
2-———~- 1
2. Dolby decoder in ;
decode mode or flat Signal from
recorder No. 2
Figure 1-4 Dotby NR Circuit Signal Processing Diagram ( continued )
1-6
amplifier mode.
L
XDA
MUUAAANL
IIT
IAIAAAA
x
A

jacks.
The
power
amplifier
signal
is
also
applied
to
the
MAIN
and/or
REMOTE
SPEAKER
Terminals
by
the
corresponding
SPEAKERS
Switch.
D.PHONO/MIC
AMPLIFIER
The
low-level
Phono/Mic
Amplifier
consists
primarily
of
a
differential-input
transistor
pair
(0201
and
Q203),
an
emitter-follower
buffer
stage
(0205),
a
high-gain
stage
(Q207),
and
an
emitter-follower
output
stage
(0209).
A
neg-
ative-feedback
network
sets
the
closed-loop
gain
of
this
operational
amplifier
at
40dB
and
establishes
the
proper
high-frequency
roll-off
points.
Other
components
in
the
feedback
network
provide
precise
Mic
and
Phono
(RIAA)
equalization.
<A
one-millivolt
input
signal
is
nominally
increased
to
100
millivolts
through
the
Phono/Mic
Amplifier.
E.
DOLBY
ENCODE/DECODE
PROCESSORS
With
the
DOLBY
Switch
set
to
REC
I,
the
DOLBY
Encoder/Decoder
(U501)
functions
as
an
encoder
and
increases
the
amplitude
of
low-level,
high-frequency
signals
10
dB.
Spec-
cifically,
portions
of
the
incoming
signal
are
applied
to
a
level-
and
frequency-sensitive
"“sidechain”
circuit
(C523,
C529,
C553, R523,
and
R527).
The
sidechain
signal
is
then
summed
with
the
main
signal
in
the
encoder/
decoder
resulting
in
the
10
dB
boost.
With
the
DOLBY
Switch
set
to
REC
II,
the
encoder/
decoder
functions
as
a
decoder
similar
to
that
described
in
the
following
paragraph.
With
the
DOLBY
Switch
set
to
either
DOLBY
FM,
PLAY,
or
REC
I,
the
Dolby
Decoder
(U503)
decreases
the
amplitude
of
low-level,
high-frequency
signals
10
dB
complementary
to
encoder
signal
processing.
Again,
portions
of
the
incoming
signal
are
applied
to
a
sidechain
circuit
(C555,
C557,
C561,
R543,
and
R545).
The
sidechain
signal
is
then
subtracted
from
the
main
signal
within
the
decoder
and,
since
the
decoder
processing
is
complementary
to
the
encoder
processing,
high-frequency
noise
am-
plitude
is
reduced
10
dB.
F.
TIMES-TEN
AMPLIFIER
The
Times-Ten
(X10)
Amplifier
is
a
non-invert-
ing
operational
amplifier
consisting
of
a
dual
linear
integrated
circuit
(U201)
and
a
constant-
current
source
(Q211)
in
the
output.
Like
the
Phono/Mic
Amplifier,
negative
feedback
sets
the
gain
of
this
amplifier
and
establishes
the
frequency
roll-off
points.
A
100-millivolt
input
signal
is
nominally
increased
to
one
voit
through
the
X10
Amplifier
(20dB
gain).
G.
ACTIVE
FILTER
NETWORK
The
Active
Filter
Network
consists
of
cascaded
filter
components
at
the
input
of
a
non-invert-
ing,
unity
gain
Filter
Amplifier
(Q213
and
Q215)
with
a
constant-current
source
(Q217)
in
the
output.
Associated
switches
connect
appropriate
filter
components
in
the
amplifier
feedback
circuit
for
a
12-dB-per-octave
rol!
off
at
either
30Hz,
5KHz,
or
9KHz.
Frequency
response
is
flat
through
the
network
when
the
filters
are
not
activated.
Characteristic
curves
for
the
Active
Filter
Network
are
shown
in
Section
2.
H.
TONE
CONTROL/TURNOVER
NETWORK
The
Tone
Control/Turnover
Network
consists
of
the
BASS,
MID
and
TREBLE
Tone
Controls
and
the
250Hz
and
4KHz
TURNOVER
circuit
connected
across
the
input
and
feedback
loop
of
the
inverting,
unity
gain
Tone
Amplifier
(U203).
Feedback
control
is
used
to
shape
the
frequency
response
at
the
Tone
Amplifier
out-
put.
With
the
TONE
Controls
raised
toyvard
“boost’’
position,
the
forward
signal
is
strongest
and
the
feedback
weakest.
When
lowered
toward
“cut’’
position,
the
TONE
Controls
attenuate
the
forward
signal
and
the
feedback
signal
is
dominant.
The
TONE
Controls
are
variable
over
a
range
of
approximately
+
1OdB.
Activating
the
250Hz
and/or
4KHz
TURN-
OVER
circuit
shifts
the
frequency
locus
(tturn-
over)
points
for
the
BASS
and/or
TRE
BLE
TONE
Controls
respectively,
as
shown
in
Sec-
tion
2.
1-7

5.
DOLBY NOISE REDUCTION
CIRCUIT
A.BASIC DOLBY PROCESS
The Model 3800 full-process Dolby Noise
Reduction (NR) Circuit enables Dolby encoding
and decoding to be performed simultaneously.
An incoming flat signal can be Dolby encoded,
recorded onto tape, monitored from the tape,
and DOLBY decoded in one operation, allowing
the end result to be immediately compared to
the original source signal.
The Dolby circuit increases the amplitude of
low-level, mid- and high-frequency signals during
recording and reduces the amplitude of these
signals by an identical amount during playback.
As a result, the playback signal is identical to
the original source signal, but the level of back-
ground noise generated by a tape or record is
greatly reduced. A Dolby FM broadcast is
subjected to the first phase of the noise
reduction process before being transmitted.
When these signals pass through the Dolby
decoder circuit, the mid- and high-frequency
noise is greatly reduced.
Section 2 contains the maintenance procedures
for the Dolby (NR) circuit in the Model 3800.
TECHNICAL SPECIFICATIONS
B. USE OF THE DOLBY (NR) CIRCUIT ASA
DYNAMIC NOISE FILTER
As previously described in the Basic Dolby
Process, high-level, high-frequency signals pass
through unchanged in both phases of the Dolby
process (encode and decode). As the level
decreases, however, filtering increases (during
playback) until the signals are 35 dB or more
below the level determined by the PLAY CAL
Controls at which point the maximum filter-
ing effect takes place. The Dolby playback
(decode) circuitry is, in effect, a variable or
dynamic noise filter.
In this regard, the Dolby playback circuitry can
be used as a substitute for a high filter. But
unlike a regular high filter whose effect on
treble response is constant at all loudness levels,
the Dolby-derived filter activates itself only
when needed, that is, only during soft passages
where background noise becomes noticeable.
To use the Dolby playback circuit as a dynamic
noise filter, set the DOLBY switch to PLAY.
The amount of filtering action is determined
by the setting of the PLAY CAL Controls. For
normal programs, adjust the PLAY CAL Con-
trols on each channel so that the average
program level, as indicated on the Dolby Level
VU Meter, indicates approximately O VU.
Technical
specifications
highlighting
performance
features
are
listed
in
Table
1-1.
Note: DOLBY circuit OFF
RATED OUTPUT LEVEL
Preamp Output
Phono Amplifier at Scope Output
GAIN
*Phono/Mic to Preamp Output
*Phono/Mic to Recording Output
*High Level Input to Preamp Output
60dB +2dB
40dB + 1.25 dB
20dB +1.0dB
Table 1-1 Performance Specifications

INPUT IMPEDANCE
Phono
47
Kohms
+
5%
Mic
8K
ohms
+
5%
High
Level
12.5
K
ohms
+
20%
Tuner
10
K
ohms
+20%
INPUT
SENSITIVITY
*Phono/Mic
1
mV
to
equal
1
Volt
at
Preamp
Output
High
Level
100
mV
to
equal
1
Volt
at
Preamp
Output
**EREQUENCY
RESPONSE
*Phono
+
0.5
dB
maximum
variation
from
RIAA
standard
Typical
variation
+0.2dB
High
Level
+
0.25
dB,
10
Hzto
20
kHz
and
+1
dB,
5
Hzto
60
kHz
into
10
k
ohm
load
or
standard
IHF
load
TOTAL
HARMONIC
DISTORTION
*Phono
0.025%
maximum,
20
Hz
to
20
kHz
at
nominal
or
rated
at
Scope
Output
into
IHF
load.
Typical
value:
0.01%
High
Level
0.25%
maximum,
20
Hz
to
20
kHz
from
nominal
output
level
up
to
6
VRMS
into
IHF
load.
Typical
value:
0.01%
INTERMODULATION
DISTORTION
Phono
0.012%
maximum
at
6
V
RMS
at
Scope
Output
into
IHF
load
Typical
value:
0.005%
at
rated
output
High
Level
0.012%
maximum
at
6
V
RMS
into
IHF
load
Typical
value:
0.003%
at
rated
output
HUM AND NOISE
(Noise
Bandwidth:
20
Hz
to
20
kHz)
Phono
Less
than
0.78
uV
equivalent
input
noise,
input
shorted
S/N
greater
than
82
dB
below
10
mV
input
High
Level
100
dB
below
rated
output,
input
terminated
into
600
ohms
Total
output
noise,
worst
case:
less
than
30
uV
CHANNEL
SEPARATION
Greater
than
40
dB,
20
Hz
to
20
kHz
*VOLUME
TRACKING
Within
2
dB
from
0
dB
to
-40
dB
attenuation
and
within
3
dB
from
-40
dB
to
-60
dB
attenuation
PREAMPLIFIER
OUTPUT
DATA
Maximum
output
before
overload
9
V
RMS
Output
Stability
Preamp
is
stable
driving
long
cables
and
capacitive
loads
with
no
evidence
of
ringing
or
overshoot
Overload
Recovery
No
DC
instability
OPERATING
POWER
REQUIREMENTS
120
V
AC,
60
Hz.
9.5
W
z
(Voltage
Operating
Range:
105
volts
to
130
volts)
at
1
kHz
**Tone Defeat Switch Out
Table
1-1
Performance
Specifications
(continued
}
1-9

( This page is intentionally left blank. )

Section
2
MAINTENANCE
1.
GENERAL
Section
2
contains
maintenance
procedures
for
service,
troubleshooting,
removal/installation,
and
repair
of
the
Model
3800.
Service
procedures
include
required
alignments,
tests,
and
adjustments
described
for
failures
or
malfunctions.
Trouble-
shooting
procedures
include
isolating
and
identify-
ing
both
mechanical
and
electrical
malfunctions.
Removal/installation
procedures
include
unit
dis-
assembly
and
reassembly
for
component
repair
or
replacement.
Performance
evaluation
tests
and
service
of
the
Model
3800
should
be
undertaken
only
by
an
experienced
technician,
one
knowledgeable
in
solid
state
preamplifiers
and
the
use
of
sensitive
test
equipment.
All
instructions
should
be
read
carefully
and
understood
fully
before
proceeding
with
any
service.
To
better
understand
the
functions
of
the
Stereo
Control
Console,
consult
the
Schematic,
Wiring,
and
Dolby
Processing
Diagrams.
Marantz
will
issue
supplementary
Technical
Service
Data
to
all
authorized
facilities
for
upgraded
service
and
product
support.
Marantz
requests
field
service
problems
and
suggestions
for
im-
provement
be
sent
to
the
Technical
Services
Manager
at
our
corporate
location.
CAUTION:
WHEN
ADJUSTING
OR
_IN-
STALLING
PARTS,
DO
NOT
OVER
TIGHTEN
MACHINE
SCREWS
OR
ADJUST
NUTS.
EX-
CESSIVE
FORCE
CAN
EASILY
DAMAGE
THE
ALUMINUM
ALLOY
PARTS.
NOTE:
Isolate
troubles
with
an
oscilloscope
commonly
used
with
standard
audio
frequen-
cies.
Measure
voltage
and
resistance
with
a
volt-ohmmeter
with
sensitivity
of
20
K
ohms-
per-volt
or
greater.
Hand
tools
should
be
small
instrument
type
to
minimize
scratching
the
finish.
2.
PREAMPLIFIER
CIRCUITS
TESTS
AND
ADJUSTMENTS
A. TEST EQUIPMENT
Test
and
adjustments
in
the
following
para-
graphs
are
based
on
the
use
of
the
Recom-
mended
Test
Equipment
listed
in
Table
2-1
or
their
equivalent.
A.C.
Power
Control
Box
and
Test
Equipment
Connection
Diagrams
are
shown
in
Figures
2-1
and
2-2
respectively.
B.
PRELIMINARY
CONDITIONS
(1)
Set
controls
on
A.C.
Power
Control
Box
as follows:
Line
Switch.
........0
eee
reese
Off
Phase
Switch......-.--220ee85
Normal
Wattmeter
Switch.
.....--+-.++ee5:
In
Autotransformer
...
Minimum
(Full
ccv)
(2)
Set
Model
3800
Panel
switches
and
con-
trols
to
their
normal
settings
except
as
noted:
Program
Selector.......----+555
AU
X
TAPE:
COPY
:'i
essoedin
oad
eee
We
des
Out
MODE
.co45
Sewer
ey
STERE
O
TAPE
MONITOR...........
SOURCE
TONE,
BALANCE.........+-5
Center
TURNOVER,FILTERS,
LOUDNESS
.0
ut
DOLBY
fot
One
ss
Shea
ds
OFF
VOLUME........
Minimum
(Full
cow)
TAPE
REC-EQ..........-0
ees
O
ut
TONE
DEFEAT.......----5
20
ees
In
RECORD
LEVEL..........--
Ful
cw
PIEAY.
CAL
teenie
ee
el
eters
ec
Fullccw
LRMETER.........----005
L
(Oust)
400
Hz
TONE.......
2
eee
ees
Out
SPEAKERS
be
oe
ise
diee
ie
eehelei
es
Out
POWER
chs
coh
bade
hess
On(I
n)
(3)
Install
shorting
plugs
in
AUX
INPUT
jc
ks.
2-1

rocco c
I
0.5 AMP I
m~ SLOW — BLOW DIRECT NORMAL
O 5)
| | OFF
| oO O O REVERSE
L/ e
O
VARIABLE
AUTO
TRANSFORMER
oat WATTMETER
|
if
|
|
|
|
I
i
|
t
AC VOLTMETER
©)
0-150V ; AC
Figure 2-1 AC Power Control Box Connection Diagram
&,
AUTO
AC
LINE
TRANSFORMER
AC
AUDIO
DISTORTION
POWER OSCILLATOR ANALYZER
CONTROL
@.)
CONNECT TO OUTPUTS
AS REQUIRED
CONNECT TO INPUTS
AS REQUIRED
OUTPUTS
INPUTS
OSCILLOS(t OPE
MODEL 3800
Figure 2-2 Test Equipment Connection Diagram, Preamplifier Circuits
2-2

EQUIPMENT ITEM
Distortion Analyzer
AC Voltmeter
Audio Oscillator
Oscilloscope
Variable Autotransformer
(0-140 VAC)
AC Wattmeter 0-150 W
Line Voltmeter
0-150 V AC
AC Power Control Box
(optional)
Shorting Plug (4)
Noise Filter (20 Hz to 20
KHz, 12 dB per-octave
rolloff, tess than 3 micro-
volts residual noise input)
MANUFACTURER AND MODEL NO.
OR EQUIVALENT
Sound Technology Model 1700A or Hewlett
Packard Model 331A or 333A
Hewlett Packard Model 400F
Sound Technology Model 1400A
Tektronix Model T-932 or T-935
Simpson Model 312, 313, or 314
Fluke Model 8000 (Digital)
Powerstat Model 116B,
Superior Electric Company
Simpson Model 1379 (Catalog No. 10970)
Simpson Model 1359 (Catalog No. 10320)
Fabricated as shown in Figure 2-1
Phono plug with 600 ohm resistor across
center pin and shell
Commerical grade
Measure total harmonic distor-
tion of preamp
Measure preamp output voltage
Audio signal source
Waveform analysis and trouble-
shooting
Voltage and resistance
measurements
Controls A.C. line voltage to
preamp
Monitor preamp power con-
sumption
Monitor A.C. line voltage to
preamp
Monitor line voltage and power
consumption
Short preamp input to eliminate
noise pickup
Measure noise.
Table 2-1 Recommended Test Equipment
C. POWER CONSUMPTION VERIFICATION
(1)
(2)
(3)
Plug Model 3800 AC Plug into AC Con-
trol Box outlet.
Set LINE Switch (AC Power Control
Box) to VARIABLE.
Observing Wattmeter, slowly rotate auto-
transformer control cw to 120 VAC. If
Wattmeter indicates more than 5 W at
any time, (or fails to indicate at all), srnut
off AC power and refer to the Trouble
Analysis section.
D. FUNCTLONAL TESTS
Perform functional tests on unit to estadf ish
the operation of all inputs, outputs and con-
trols as specified. Reset Model 3800 conrols
2-3

to their normal settings upon completion of the
functional tests both channels.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(1)
(2)
2-4
For low level (Phono or Mic) input tests,
apply a 1 kHz, 10 mV audio signal to
PHONO INPUT |. Depress PHONO |
Switch.
Set Distortion Analyzer controls for AC
VTVM and monitor output at SCOPE or
TAPE OUTPUT Jack. Output should be
approximately 1 V rms.
Repeat at PHONO INPUT 2, depress
PHONO 2/MIC Switch.
Without changing oscillator output level,
disconnect from PHONO INPUT 2 and
reconnect in front at MICROPHONE Jack.
Output should remain at approximately
1 Vrms.
For high level (Tuner, Aux, or Tape) in-
puts, turn preamp power off, set oscilla-
tor to 1 kHz, 300 mV rms output.
Connect to TUNER INPUT Jack. Re-
connect Distortion Analyzer to PREAMP-
LIFIER (PREAMP) OUTPUT Jack.
Turn preamp power on, turn VOLUME
Control to maximum, depress TUNER
Switch. Output should be approximately
3 V rms.
Without
changing
any
connections
other
than
inputs,
check
AUX,
TAPE
1,
and
TAPE
2
OUTPUTS
as
described
in
Step
(6).
Output
level
should
remain
at
approximately
3
V
rms.
MAXIMUM
VOLTAGE
OUTPUT
Depress
AUX
Switch.
Connect
oscillator
to
AUX
INPUT
Jack.
Monitor
signal
at
PREAMP
OUTPUT
Jack
with
oscilloscope
and
distortion
analyzer
controls
set
for
AC
VTVM.
Turn
VOLUME
to
maximum.
Set oscillator frequency to 1 kHz and
increase oscillator output to the point of
just below clipping. VTVM should indi-
cate at least 9 V rms.
(1)
(2)
H.
TOTAL HARMONIC DISTORTION (THD)
With
preamp
VOLUME
Control
turned
to
maximum,
check
THD
at
AUX
INPUT
Jack
at
20
Hz,
2
kHz,
and
20
kHz
(3
V
rms
output).
THD
should
be
less
than
0.025
percent.
Change input to PHONO Jack and depress
PHONO Switch. Adjust oscillator for
3 Vrms at TAPE OUTPUT Jack. Check
THD at 20 Hz, 2 kHz, and 20 kHz. THD
should be less than 0.025 percent.
HUM AND NOISE
Insert
phono
shorting
plug
into
each
PHONO
and
AUX
INPUT
Jack.
Switch
in
bandpass
filter
control.
Turn VOLUME Control to maximum and
depress PHONO Switch. Noise output
should indicate less than 780 microvolts
measured at PREAMP OUTPUT Jack.
Depress
AUX
Switch.
Noise
output
should
indicate
less
than
30
microvolts
measured
at
PREAMP
OUTPUT
Jack.
FREQUENCY
RESPONSE
(PHONO/MIC)
—
Refer
to
Figure
2-3
RIAA
Equalization
Curve
and
Standards
to
verify
unit
conformance.
(1)
(2)
For
Phono
frequency
response
apply
a
1
kHz
signal
to
PHONO
INPUT
Jack.
Connect
AC
VTVM
to
PREAMP
OUTPUT
Jack.
Set
oscillator
output
for
0
dB
indication
on
VTVM.
Check
output
level
at
the
following
fre-
quencies
+
0.5
dB:
PONAE
8
ep
ce
alg
athe
aia
¥
+19.30
dB
TOOTS
lace
te
wted
wee
ae
+13.11
dB
BOO
IAT:
wiseaisieie:
2
deatawede
nets
+3.81
dB
2
KRE
So
Seun
heey
kG
to
-2.61
dB
TOUR
Ze
soe
rsse
eae
ataalt
anaes
-13.75
dB
COKE
2
aan
ca
a
da
vee
as
-19.60
dB
For
Mic
frequency
response
appiy
a
1
kHz
signal
to
MICROPHONE
Jack
(front
panel).
Depress
2/MIC
Switch.
Set
oscillator
output
to
0
dB
as
measy
sed
at
PREAMP OUTPUT
Jack.

(4)
(1)
(2)
(3)
(4)
Reduce oscillator frequency to 30 Hz.
Output should be O dB (+ 0.75 dB).
Increase oscillator frequency to 11.5 kHz.
Output should be O dB (+ O GB, -4 dB).
HIGH LEVEL SEPARATION
Connect oscillator to left channel! AUX
INPUT Jack. Insert a shorting plug into
right channel AUX INPUT Jack. Monitor
signal at PREAMP OUTPUT Jack with
AC VTVM.
Set oscillator frequency to 20 Hz. Set
oscillator level for 0 dB, 3 V rms output
as indicated on the VT VM.
Observe the output of the undriven chan-
nel on the VTVM. Output should be at
least 40 dB below the O dB reference level
indicating a 40 dB left - to - right channel
separation.
Repeat test on right channel.
(2)
(3)
(4)
(5)
RIAA NAB DISK REPRODUCING STD.
20 KHz . . ~19.60 dB
15 KHz . . -17.17 dB
14 KHz . . 16.64 dB
13 KHz . . 15.95 dB
12 KHz . . 15.28 dB
11 KHz . . -14.55 dB
10 KHz . . =13.75 dB
9 KHz. . -12.88 dB
8 KHz . . =11.91 dB
7 KHz . . —10.85 dB
6 KHz . . — 9.62 dB
5 KHz . . = 8.23 dB
4KHz...... . . = 6.64¢B
3KHz...... . .=—4.76dB
2KHz..... . . . = 2.61dB
1000. ....... +. 0,00dB
700. . vee + 1.23 dB
400. + 3814B
300. ........ . + 553 4B
200. ...... . . + 8.22 dB
100... 2...) . #13.11dB
7... . . 2... +16.314 dB
50. ..... . . . +16.96 dB
30. ..... . . . +18.61 dB
20 Hz . +19.30 dB
Figure 2-3 RIAA Equalization Curve and Standard
FILTERS (Figure 2-4)
Connect oscillator to AUX INPUT Jack.
Depress AUX Selector Pushswitch. Con-
nect AC VTVM to PREAMP OUTPUT
Jack.
To establish a reference level, set osci Ila-
tor frequency to 1 kHz, 0 dB as measured
on the VTVM.
Depress 9 kHz FILTER Switch. With
oscillator switched to 9 kHz input, out-
put level should drop 3 dB (+ 1.25 4B).
Depress and release FILTER switch.
Depress 5 kHz FILTER Switch. With
oscillator switched to 5 kHz, output
should drop 3 dB (+ 1.25 dB). Depress
and release FILTER Switch.
Depress 30 Hz FILTER Switch. With
oscillator switch set to 30 Hz, siy nal
should drop 3 dB (+ 0.75 dB). Depress
and release FILTER Switch.
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